Centralized traffic controlling system for railroads



April 12, 193 8.

W. D. HAI LES CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed June 1, 1936 8 Sheets-Sheet 1 I 1 Wm F llllllllllllllllllllll v F 30 253 2.3 co usv 12 April 12, 1938". w; D. HAILES I 2,114,001

CENTRALIZ ED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed June 1, 1936 8 Sheets-Sheet 2 v m a: Q 3 i 8 Sheets-Sheet 3 W. D. HAILES Filed June 1, 1956 CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS April 12, 1938.

@220 ATTORNEIY w. D. HAILES' 2,114,001

Filed June 1, 1956 8 hee he t 4 April 12, 1938.

. CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS fiw ia .EN mm x 1 ?8 2s 8 ES? N2 5 o2 +s v AL vmQ N .n BHNHEP EHE BS a 2B u m 1 N o l a T 2 EEE w T E Gig wmw fi lg b? $3 WW Sm ws,n wr m m z m v R. n n I E B. u u u u n u mm .23 u u n n u n 4 (N u 0 pm n m 2 n B 3 mm m u E m w sbz m m vm Bum 02 MN m m s u a .n m -m u m 4 1 L4 1 1 1 H4 .1 .T L. r W .r r .r NJ may mi N u E u Em. N n u m u m i E April 12, 1938. w. D. HAILES 2,114,001

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed June 1, 1936 8 Sheets-Sheet 5 m $2 $2 232 2: N2 N9 Al: A; R E2: 2 2 w mww u N T T N2 3252mm Mm E .ET u u m HQEQ EE m 3 T wfil B ,V u n u h u M f? m m u Jmlt Nv m m n T m u u m u t? 10 MN u n u W m m 8 ww mm m m v n n u u m u u m u u m u K. e u 1... 1a. 1 in L- LI r \i .i .3 m3 u mm um mm 2 3 fi r m a a a u u u n n. 9.9L

April 12, 1938. V L g 2,114,001

CENTR ALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed June 1, 1936- a Sheets-Sheet 7 E IGQZQA; z 1 1 1 LE z z .L E 1 2 Conl'rals 1 Sher? an and on Long off and +0n 5hor1 OFF and -On Long .off and -On n9 OFF or? Off 'ITme of on Indicah'ons AC. or No AC on The. On Ind iaaT/on AC. or No AC- I 277 27a 27a T 9 Y INVENTOR' 11/. AZ. 14m Z WAZ ATTORNEY W. D. HAILES April 12, 1938.

CENTRALIZED TRAFFIC QONTROLLING SYSTEM FOR RAILRCADS I Filed June 1, 1956 '8 Sheets-Sheet 8 ATTORN'EY Patented Apr. 12, 1938 OENTRALIZED TRAFFIG CONTROLLING SYSTEM FOR RAILROADS William D. Hailes, Brighton, N. Y., assignor to General Railway Signal Company, Rochester,

Application June 1, 1936, Serial No. 82,711

30 Claims.

This invention relates to Centralized traffic controlling systems for railroads and itmore particularly pertains to a means for transmitting and registering controls and indications in a communication system of the multiple impulse or code type. l

The switches and signals are distributed throughout the territory in such a system and those located relatively near or adjacent each other, together with the apparatus provided to govern these switches and signals, are conveniently referred to as comprising a field station. The communication system is provided to interconnect the control office with the several, field the several field stations in series. The conductors of this line circuit are conveniently referred to in the drawings as line conductor L and return 30 conductor R. This two-Wire line circuit is normally energized from a source of current located in the control office, with the line relays and other devices connected in series with the line wires at the field stations and with the line and return 35 conductors permanently connected together at the end station to form a closed circuit loop.

The line circuit is so arranged that any field station in the series may initiate the communication system into a cycle of operations, during 40 which indications are transmitted from the initiating field station to the control ofilce. These indications comprise multiple impulses making up a code combination, which effects the registration of thetransmitting field station in the con- 45 trol office and the transmission of indications in accordance with track, and signal conditions at the transmitting station. ,7

The line circuit is also arranged so that the control office may initiate the operation of, the 50 communication system, during which multiple impulses are transmitted making'up a codev which is efiective to select a desired station and to transmit controls thereto.

during each of which transmission of controls and/or transmission of indications may occur. When controls are transmitted, a station selective code is first applied to the line circuit for selecting the particular station with which communication is desired and then the controls are transmitted to that station. Similarly, when indications are transmitted the particular field station transmitting such indications first transmits a station registering code for identifying this station in the control ofiice and then the indications are transmitted from this station to the control office.

I For the transmission of controls, a predetermined number of impulses of selected polarities are applied to the line circuit, each impulse operating step-by-step apparatus in the'control office and at the field stations through a cycle of operation, irrespective of the character of the impulses. The time spaces between successive impulses are varied in length in accordance with the controls to be transmitted so that these time spaces are comparatively long or short and they are combined with the polar impulses to make up the code for selecting stations and for transmitting controls thereto.

For the transmission of indications, the impulses themselves are varied in length to provide normally long impulses or abnormally short 1m,- pulses at each step of the stepping mechanism.

' In addition to the variation in length of impulses,

alternating current is applied to the line circuit, both during the impulse periods and the time spaces between impulse periods for providing additional selections for indication transmission. This feature of applying or superimposing alternating current on the line circuit for the purpose of transmitting indications over a stepping circuit transmitting stepping impulses of direct current is broadly shown in Fig. 4 of the prior application of Hailes and DeLong. Ser. No. 526,674. filed March 31, 1931, and no claim is made herein to any invention disclosed in said prior application. Briefly the indication codes comprise short or long impulses, alternating current or no alternating current superimposed on the line circuit during the impulse periods and alternating current or no alternating current superimposed on the line circuit during the time space periods.

For convenience in describing the operation of this system the energized or impulse periods from the control oifice source of direct current will be referred to as the on periods and the deenergized or time spaces between direct current imlevers. Similarly, one or more signal control levers may be provided, but for convenience'no signal lever is illustrated, since the control of switchesby the illustrated switch levers is typical t of the control of signals when signal levers are.

provided.

A single OS indicating lamp is illustrated for the purpose of indicating the method of transmitting an OS indication from a particular field station and it will be understood that additional lamps of this type may be provided asrequired.

A plurality of code jumpers are selected by the circuits controlled by the CD relays and those illustrated by reference characters ;I0 and II,

selected by the illustrated CD relay in Fig. 1C,

purpose of providing the proper polarity of en- 1 ergization of the line circuit during the transmission of control impulses. With relay PC energized and relay NC deenergized a impulse is applied to the line circuit from battery LB whenthe impulsing relays'effect the closure of the line circuit. Withrelay PC deenergized and relay NC energized, then a impulse is applied to the line circuit upon the closure of the line circuit by the impulsing relays. Code sending relay LG is for the purpose of rendering a time space comparatively long in duration, when this relay is picked up. If relay LG is not picked up at a particular step of the cycle, then the time space is comparatively short in duration.

Pilot relays lPT to 4PT inclusive are polar re- 1 lays of the magnetic stick type and'are positioned line circuit during a cycle of operations.

0C is a cycle controlling relay, being picked up in accordance with a' station identifying code received in the control office during a duplex cycle or a cycle during which indications alone are being transmitted. A polar relay of the magnetic stick type operates itscontacts to normal and reverse positions in response to current of normal and reverse directions respectively through its winding and the contacts are magnetically maintained in their last operated position after'the' winding is deenergized. Relays 1\ /lF, MFZ, and

MBZ are the indication code receiving relays which are conditioned during the steps ofa cycleduring which indications are transmitted. Relay MF registers the length of the on indication at relay MBZ registers whether or not alternating current is superimposed on the line circuit during the off period at each step.

Impulse relays l E to 5E, inclusive, are for the purpose of timing the closure and opening of the atthe start of any cycle and maintained picked up until the end of the cycle, the purpose of which will be pointed out later in the description. Line relay F is included in the line circuit at the control office and is for the purpose of repeating each energization and deenergization of the line from battery LB, irrespective of thepolarity of such energization. Line repeating relay FP repeats each energization of relay F after a cycle of operations is initiated, but does not repeat the normal energization of line relay F i when the system is in its condition of rest.

Slow-acting'relays SA, SB, and SD are picked up when Relay I at the beginning of each cycle, remain up throughout the cycle'and are dropped at the end of the cycle. Relay SC is normally picked up, is

dropped out at the beginning of each cycle and again picked up during the clearing out period ing the ofifperiods and relay VP being shifted in position during each on period.

Control cycle relay C is provided for marking a cycle of operations for the transmission of controls, this relay being'picked up during the initiating period of acontrol cycle and remaining up until the clearing out period at the end of such a cycle. Field station control relay CF is for the purpose of marking a cycle of operations for the transmission of indications, this relay being picked up during the initiating period of a cycle for the transmission of indications and remaining up until the clearing out period of such a cycle.. During a duplex cycle, when controls and indications are both being transmitted, relays C' and CF are both picked up. Relay FPA'repeats the deenergized conditions of relay FP, that is, relay FPA is picked upduring each deenergizationof relay FF and is dropped-out at each energization of relay FP, during a cycle of operations.

'A vacuum tube detecting device is illustrated in i the upper portion of Fig. 1B and is for the purpose of detecting alternating current impulses superimposed on the line circuit and for translating these impulses into direct current impulses for operating the MFZ and MBZ relays in a manner which will be fully described. This detecting device comprises vacuum tubes IVT and 2VT with their associated in-put transformers IIT and ZIT respectively. Out-put transformer IOT in the out-put of tube 2VT has its secondary connected to the MBZ and MFZ relays through rectifiers IRC and 2RC. Various resistances, inductances and condensers are included in the line and vacuum tube circuits, the purpose of which will be evident from the following description. It is assumed that the filaments of thevacuum tubes are energized from a source of battery AB and the plates are energized from a source of battery'BB, although it will be obvious that a power transformer may be used for energizing these tube circuits by the usual rectified current arrangement if desired.

Field station equipment.'1'he field station illustrated in Figs. 2, 2A, and 2B is typical ofall stations of the system and may be adapted for use at the first, second or any other location by merely altering certain code jumpers to arrange for the desired codes. For convenience in the description, this field station has been specifically illustrated as being the first of the series by reason of the distinctive exponents employed. Likewise the end statio-nillustrated in Fig. 2B-is assumed to be the second in the series by reason of the distinctive exponents employed, but it will be understood that other stations maybe interposed between the control ofiiceand the first stathefirst station and the second tion and between station.

ated from one extreme lockedpcsition to the other by means of switch machines 13M? and ZSM respectively.

Switch'machine I'SM is operated by switch machine ccntrolrelay ISMR and switch machine 2SM is :operated by switch machine control relay-23MB These'control relays are of the maitwo-position polar magnetic 'stick type and are governed from the control oflice through the medium of the communication system herein disclosed. Two control. relays areillustrated for the purpose of indicating how two track switches 5u'may be controlled at a single step of the stepi ping bank. 'These switch control relays control the operation 'of the associated switch machines by energizing their normal or reverse operating wires from a'local source of current, it being aszoiisumed that each switchma'chine is operated to its normal locked-position when'the polar con-' 'tacts of the associateds'witch control relay are actuated to the'right and when these contacts are acuated to the left the associated switch" ma- 251fchine is operated to its reverse locked position.

It will be understoodthat this control preferably includes suitable: approach locking means and such other automatic signalling circuits as are usually employed in practice, but which are not ao' shown in the presentdisclosure for the sake of" simplicity.

Suitable signals (not shown) are associated with the illustrated track switches for governing traffic thereover and are provided with autorelays may be operated in a manner similar to the operation of the switch control relays, as

later described.

1:, For the purpose of illustrating how indications are transmitted by timing the on periods of a cycle and by superimposing alternating current on the line circuit duringtheon and off periods, code jumpers 2H), 21 I, H2, and 2l3 are crprovided. For the purpose of illustrating how indications are transmitted from a registered station, track relay TR. and signal repeating-re lay M are illustrated.

The communication part of the system includes i2polar line relay F and its quick-acting repeating relay FP Slow-acting relays SA and 813 are for a purpose similar to that explained in con-,

nection with corresponding relays in the control ofiice, these relays being picked up atthe-begina ning of a cycle of operations, maintainedpicked up throughout the cycle and dropped out during the clearing-out period at the end of the cycle. The field station includes a bank of stepping relays, comprising relays IV 2V 3V and VP? ':which correspcndto similar relays inthe control cflice. These relays are operated by circuits similar to the circuits for corresponding relays in the control office and in synchronism therewith, therefore it is believed unnecessary to illus-' atratethedetailedcircuits of the field static stepping relay bank. 1

For the purpose of illustrating the selection of a stationfor the transmission of controls, relay SO and relay 808- have been shown. Afield z =change relay CH is shown to illustrate how. a

cycle of operations is initiated from a field station.

For the purpose of illustrating the manner of determining when a field station is to transmit its indications, lock-out relay L is employed. 5

When relay L0 is picked up during a cycle of operationsto permit the field station to transmit, the impulses applied-to the line circuit (in the control office) are left normally long or are made abnormally short by the field station relay PF". During the transmission of indications the picking up of relay L0 is also effective to permit the control of indication transmitting relays'FZ and BZ in accordance with whether or not'alternating current is to be allowed to flow over the line circuit to the control office or whether it is to be shunted away from the line circuit leading to the control oflice by a shunt provided at the transmitting field station. Relay PF converts a normally long direct current impulse applied bythe ofiice to the control line circuit,

to an abnormally short impulse in accordance with indications to be transmitted from a station marked by relay LO being picked up.

-Relays 'PT and PB control the continuity of the line circuit for purposes which will be described in detail. A filter, comprising inductances 2IN MN and condensers 2C and 1C is'connected in the line circuit and is for the purpose of preventing or permitting the flow of alternating current over the line circuit to the ofilce in Operation The system of the present invention is normally in a condition of rest, from which it may be initiated'into a cycle of operations either from the control office or from any one of the field stations when there are new controls or new indications, respectively, ready to be transmitted.

If new controls for several difierent field stations' are ready for-transmission at substantially the same time, they are transmitted on separate cycles, one station for each cycle. Similarly, if several field stations have indications ready for transmission at the same time, they are trans- 5 mitted from such field stations to the control office, one station for each cycle.

'Itmay happen that there are new controls and new indications ready to be transmitted at the same time and in such instances controls are transmitted to a selected fieldstation simultaneously with the transmission of indications from the same or some other field station during the same cycle. I

Irrespective of whether a cycle isto be for the transmission of controls and/or the transmission of indications, a predetermined number of impulses areplaced upon the line circuit to accomplish the step-by-step operation of the stepping relay banks. These impulses are timespaced, that is, they are separated by time spaces andthe lengthsof these time spaces are varied in =accordance with the control code to be transmitted. During an indication cycle when no controls are being transmitted the time spaces between impulses are all comparatively short. When a cycle is initiated for the transmission of controls the character of the impulses placed upon the line circuit is determined in accordance with the station to be selected and the controls to be transmitted. The lengths of the time spaces and the character of the impulses aredetermined by code jumpersxfor selecting the station and control levers for transmitting controls to the selected station.

During acycle of operations initiated for the transmission of indications alone, the character of the impulses placed upon the line circuit and the lengths of the spaces between impulses are such that no station will be selected, these impulses merely causing the step-by-step operations of the control office stepping relay bank and the particular field station stepping relay bank which is transmitting. A series of impulses which selects no station for an out-bound call is re- Such a ferred to as a control phantom code. code in the present embodiment comprises one or more impulses and one or more normally short-time spaces, the number of which is determined by the number of station selection steps.

I When a cycle of operations is initiated from a field station for the transmission of indications,

a plurality of impulses are placed upon the line circuit in the control office to cause the stepby-step operations of the stepping relay banks and these impulses are made normally long or [abnormally short to make up a'portion of the code determined by the-field station transmitting and in accordance with indications to be transmitted fromthe station which is transmitting. In addition to the length of the im- ,by the transmitting field circuit to thecontrol oflice. Alternating current pulses, the indication code is further made up station permitting or preventing alternating current fiow over the line is superimposed on the line circuit at the end station in one embodiment and at the transmitting station in the other embodiment.

Normal at rest conditions.--The two-wire line is normally energized over a circuit which may be traced from the terminal of battery LB (Fig. 1A), back contact 20 of relay PC, front contact 2 of relay 'NC, conductor 22, inductance lIN, return line conductor R, inductance lIN return conductor R back contact 3230f relay L secondary Winding of transformer TF back contact 32!] of relay PF back contact 32! of relay PR inductances 3IN and 21181 in series, winding of relay F line conductor L back contact 220 of relay PF back contact 22! of relay PB windings of inductances 3IN 'and 2IN in series, winding-of relay F line conductor LQinductance ZIN,

winding of relay F, conductor I58, back contact 30 of relay IE, back contact3lof relay 2E, back contact 32 of relay 4E, back contact 33 of relay LG, front contact 34 of relay NC and back contact 35 of relay PC to the terminal of battery LB. The current flow in this direction will be conveniently referred to as and it is effective to maintain relay F in its picked up position and relays F and F with their polar con- I of relay CF, conductor 39, NC -bus 40 and winding of relay NC to Relay SC in the control office is normally energized over an obvious circuit completed at back contact M of relay SB.

'At the station, relay PT is normally energized I over a circuit extending from contact 222 of relay F in its left hand position, back contact 223 of relay SE and winding of relayPT to Relay 01-1 at the field station is assumed to be normally energized over a circuit not shown and it will be assumed that this relay is deenergized when the associated field station has,

new indications to transmit. Track relay TR. (Fig. 2A) is illustrated in its picked up position, it being assumed that the track section with which it is associated is unoccupied. Relay M is shownpicked up, it being assumed that all signals associated with the illustrated track section are at stop.

Manual start.--With the system in a condi-s tion of rest it may be manually initiated into a cycle for the transmission of controls. Whenever such a cycle is desired the operator first positions the control levers for the field station which he desires to select and then actuates? the-starting button associated with this 'station.

For the purpose of considering the operation of the present system it will be assumedv that levers ISM'L and 2SML are actuated to their normal positions (as indicated) for operating the;

associated track switches (Fig. 2B) to their normal locked positions and that starting button STB is actuated to start the cycle of operations.

The actuation of button STB causes relay CD .to be picked up and stuck up until the end of the 'cycle. ,The actuation'oi button STB also applies to C bus 42, which causes current to flow over this bus, back contact d3 of .relay 00, back contact 44 of relay SB and lower winding of relay C to Relay C is picked up and closes a stick circuit for itself extending from front contact 45 of relay SC, front contact 46 and upper winding of relay C to The picki ng up of relay C prevents the energization of relay CF, after the start of'this cycle, by. opening back contact 41.3

The picking up of relay C closes a circuit for picking up relay 00 which extends from back contact 36 of relay SD, front contact 31 of relay C and winding of relay O0 to 0-). The picking up of relay '0 de-energizes relay NC by opening the above described normal energizing circuit at back contact 31. The opening of back contact 43 of relay 00 opens the above described pick-up circuit of relay C, so. that the energization of this relay is held off at the end of the cycle for purposes which will be later described.

A circuit is now closed for picking up ,relay PC which extends from front contact'48. of relay 00, front contact 49 of relayC, back contact of relay 3V, back contact 52 ofrelay 2V, back contact 53 of relay IV, PC bus 54 and winding of relay PC to The dropping of relay NC and the picking up of relay PC changes,

the energization of the line circuit from to by means of. pole-changing contacts 20, 2|,

34, and 35 of these relays. This change in polarity of energization of the line circuit momentarily drops relay F, which is again imme-;,

diately picked up and is ineffective. This reenergization of the line circuit reverses the positions of the polar contacts of the line relays at the stations from their left hand positions '-to their right hand dotted positions. Relay 3E frontcontact 55 of relay C, conductor I 6!),back contact- 56 of relay 2E and-winding of relay 3E to- I Y Acircuit isnow closed for picking up relay FP which extends-from front contact 5'! of relay PC, conductor 58, front contact 59 of relay F and winding of relay FP'to A circuit is now closed for picking up relay SA which extends from applied to conductor 58 over the above described. circuit and extending through front contact 60' of relay FP to the winding of relay SA. A circuit is closed for picking up relay SB which extends from front contact 6| of relay SA and winding of relay SB to Relay SB opens the normally energized circuit for relay SC at back contact 4I;' which causes the de-energization of relay SC. Another stick circuit is closed for relay C at front contact 93 of relay SB, which is effective before relay SC drops and opens its front'contact 45.

Relay SD is picked up over an obvious circuit closed at back contact 62 of-relay SC. The closure of, front contact 63 of relay SB applies energy to the plate circuits of the vacuum' tubes and since this relay is maintained in its 'picked up position throughout the following cycle, the platecircuits are maintained energized during the cycle. The picking up of-relay SD opens the pick-up circuit for relay CF at'back contact for the purpose of holding off the picking up of relay CF until all of the relays have been restored to normal at the end of the cycle. The opening of back contact 44 of 'relay SB also opens the above described pick-up circuit for relay C so that the pick-up' operation-of this relay is held'off at the end of the cycle for ,a

purpose which will be later described. 7

It will T be understood that the intermittent energization of relay SA by contact fifl' ofrelay FT; supplemented during a long off by contact I2 of-relay IE, are at such a rate thatr'elay SAdoes not have time to drop out during an operating cycle; energy is applied to conductor 58 at front "contact 5 of relay SD to supplement that at contact 51-Ofr relay PC,'since. contact 51 may not beclosed'during each on a period.

Stepping and impulsin'g operations-Relay VP is p-icked up over" a circuit extending from frontcont'act 65. of relay SD, frontcontact 66 of relay FP, back contacts 61;-6B and 69 of relays 3V, 2V, and -IV respectively and winding of relay VP to Relay VP closes a first stick circuit for itself which extends from front contact 65-of relay-SD, front contact of relay VP and over the -remainderof. the above described circuit to the winding; of relay Relay IE is now' pickedup over'a circuit extending :from front contact 65 of relay SD, back contacts 'II-,;72- and 11 3 of relays 3V,

2V, and IV respectively,' front contact "I4 of relay conductor NH, and winding of relay lE-to 'Relay "2E is pickedup over an obvious circuit closed at front contact I5 of relay IE. The picking up of relay SD opens I the above described pick-up circuit'for relay 0C, but before 00 has'time'to release, a stick circuit is closed from front contact 36 of'relay SD, front contact 9 of relay 00, conductor I62, front contact 8 of relay 2E, conductor I63. andwinding of relay O0 to Relay 0C. is held up throughout i the cycle by is picked up over a circuit which extends from means'o-f this. stick circuit and'the onein multiple with contact: 8 completed atv front contact I of; relay 5E.

' Thepicking up .;of relay. 2E opens the above describedenergizing circuit for= relay 3E at back contact 56, which :drops relay 3E and a circuit is closed for picking uprelay 4E which extends froml(+), back contact 'IB of relay 3E, back contact I! 'ofrelay MF, conductor I33, front contact 18 of relay FP, conductor I64 and winding of relay 4E to Relay 4E closes a stick circuit for itself whichextends from. back contactclfi of relay 3E," front contact 19 and winding of relay 4E to ,(-c). Relay 4E closes an obvious pick-up circuit for relay SE at front contact 80'.

The picking up of relay 4E opens the line circuit at back contact 32 which de-energizes' the line and allows relay F to drop. The drop- =ping of .relay F causes the dropping of relay:

FP by opening front contact 59. The dropping of relay FP closes a second stick circuit for relay VP which extends from front contact 65. of-relay. SD, back contact 66 of relay FP, frontycontact 8| and winding of relay VP A circuit is now closed for picking up relay IV which extendsfrom back contact 82 of relay FP, front contact 83 of" relay SD, front contact 84 of relay VP, back contact 85 of relay 2V and winding of relay IV to Relay IV closes a stick circuit for itself which extends from front contact 86 of relay SD, front contact 8'! and Winding of relay IV to Since front contact 4I- of relay SB is closed,.. it will be obvious" that the intermittent closing and, opening'of" back contact of relay FP causes the intermittent energization and de-energization of relay FPA, but-since this operation of; relay .FPAhas no function during a control cycle, its operation at each step will not be pointed *out.

The picking-up of relay IV opens the above described circuit of relay IE at back contact 13,

- which allows relay IE'to drop, which inturn plied to the line circuit is (for reasons later described), thereforerelay NC will be assumed picked up so that the line circuit is energized when relay 4E drops and closes its back contact over a circuitincluding backcontacts 3I- and 30 of relays 2E and IE respectively to the winding of relay F. This again picks up relays F and FF as previously described. Relay VP is now deenergized because its first stick circuit is open at back contact 69 of relay IV and its second stick circuit is open at back contact 66 of relay FP. The dropping of relay VP completes the above described pick-up circuit for relay IE, which now extends through front contact 13 of relay IV and back contact I4 of relay VP and the picking up of relay IE effects the picking up of relay 2E, j the dropping of relay 3E and the picking up of relay FP, front contact 83.0f relay SD, back contact 84 of relay VP, back contact 89 of relay 3V,

front contact 90 of relay IV and winding of relay 2V to Relay 2V closes an obvious stick circuit for itself at its front contact 9|. The opening of back contact I2 of relay'2V de-energizes relay IE, which in turn effects the dropping of relay 2E, the picking up of relay 3E and the drop-- ping of relays 4E and- 5E.

Relay 4E closes up the line circuitat its back contact 32 and it will be assumed that relay PC is in, its picked up position for applying a impulse to the line circuit at this time. The energy applied to the line circuit effects the picking up of relays F and PP and relay VP is now picked up over a circuit extending from front contact 65 of relay SD, front contact 66 of relay FP, backcontact 61 of relay 3V, front contact -68 of relay 2V and winding of relay VP to Relay VP again closesits first stick circuit as previously described. Relay IE is now energized because of closed front contact I2 of relay 2V and closed front contact 14 of relay VP and relay IE in turn effects the picking up of relay 2E, the dropping of relay 3E and the picking up of relays 4E and 5E in a manner previously described. 1

Relay 4E opens up the line circuit at back contact 32 and the de-energiz'ation of the line circuit effects the dropping of relays F and PP. The above described second stick circuit for relay VP is now completed and a pick-up circuit is completed for relay 3V which extends from back contact 82 of relay FP, front contact 83 of relay SD, front contact 84 of relay VP, front contact 85 of relay 2V and winding of relay 3V to Relay 3V closesan obvious stick circuit for itself at its front contact 92.

Relay IE is now de-energized because of open back contact 'II and this relay effects in turn the de-energization of relay 2E, the energization of relay 3E and the de-energization of relays 4E and 5E. The dropping of relay' IE. again energizes the line circuit by closing back contact 32 and it will be assumed that relay NC is picked up for making the next impulse The energization of the line circuit efiects the picking upof relays F and PP and the dropping of relay VP in a manner previously described. The dropping of relay VP closes the pick-up circuit for relay IEat back contact I4, which is completed through front contact 'II of relay 3V. Relay 2E is now picked up, relay 3E is dropped and relays 4E and 5151 are picked up in the manner previously described.

The picking up of relay 4E again de-energizes the line circuit, which effects the'dropping of relays F and FF. Since there are no more stepping relays to be picked up, the energizing circuit for relay IE is not interrupted and this relay remains in its picked up position for maintaining relay 2E picked up. Relay-3E is down and relays 4E and 5E are up and stay up for a comparatively long interval of time which effects the clearing out of the system.

During this clearing out period, relay SA is dropped because front contact 60 of relay FP remains open for an extended period of time. The dropping of relay SA effects the dropping of relay SB because of open frontcontact 6|, the'dropping of relay SB effects the picking up of relay SC because of closed back contact 4I= and the picking up of relay SC effects the dropping of relay SD because of open back contact 62.

Relay C is de-energized during the clearingout period because relay SB opens its front contact 93 before relay SC closes its front contact 45, which-is effective to open the stick circuit for relay/C fora period of time sufficient to dropout this relay. The dropping of relay SD opens the energizing circuit for relay IE at front contact 65, which allows relay IE to-release, after which relay 2E is'released, relay 3E is picked up and relays 4E and'5E are dropped out in the manner previously described. I The dropping of. relay SD de-energizes'the stick circuits of the stepping relays at. open front contact"85 which effects the dropping of these relays. The dropping of relay SD also opens the stick circuit of relay DC at front contact '35 a which effects thedropping of relay 0C. Relay 3E: is de-energized by the opening of frontcontact 55 of relay OC. The dropping of relay SD' completes the above described pick-up circuit for relay NC at'back contact '38, so that relay NC 'is'120- picked up forapplying e'nergyto the line circuit, which in turn picks up relay F and the system is placed in its normalcondition.

I Selection of control code.'Ihe step-by-step and impulsing operations, effective in response to the initiation of the system fromzthe control office, have been pointed out and it' 'was assumed that'these impulses applied to the line circuit were of certain polarities; It will noW' be explained how thesepolarities are: determined and '30 also how the lengths of the time spaces between impulses are determinedall in accordance with 'Jumper II connect'edas shown determines that the first off period (following the conditioning onperiod) will be comparatively long; This is effected by the picking up of relay LG'when re- I lay IV is picked up in the'first off period, over a circuit extending from(+), frontc'o'ntact 11.8

of relay OC, front contact49 of relay C, front contact of relay VP, back contact 23 of relay 2V, front contact 24 of relay IV, conductor "25, front contact 26 of 'relay CD, jumper II, LGbusiififl 21, winding of relay LG, and-front contact 28 of relay5E to The' dropping of relay 4E and the closure of itsb'ack contact 32 during the first off period is ineffective to energize the line Y circuit because of open back contact 33 of relay-' LG. When relay 5E drops during the first off fperiod'the above described circuit for relay LG "is opened at front contact 28, which allows relay I LG to drop away, but since this relay is of the slow release type, a comparatively long interval -of time will be measured off before relay LG closes its back contact 33.

When back contact as is closed the line is en- "ergized to mark the end of the first o if period but in this instancethe first off period is re ndered comparatively long. In the event that jumper II isin its alternate dotted line position, relay LG is not picked up and the line circuit is energized by the closure of back contact 32 when relay 4E drops, which render's'the first 91f period comparatively short.

The polarity of the first on impulseffollowin'gthe first off period) is determined by the position of jumper Ill. 'With j umper I0 inthe position shown, relay NC is picked up during the tacts. 20, 2|, 34 and 35 efiectthe-application'o-f a impulse to the line circuit. In the event that jumper: Ill-is in its alternate dotted lineposition, then the above described circuit extends through the winding of relay PC instead ofrelay NC,',which would pick up relay PC and prevent the picking up of relay NC, thus resulting in a impulse being applied to the line circuit.

It will thus be seen that the code sending relays are positioned upon the picking up of the stepping relays during the off periods, while the line circuit is de-energized, in readiness for energizing the line, with the selected polarity at thebeginning of the next on period. Although it is assumed that the station is selected on a single step in the present embodiment, thus requiring only code jumpers I and II, it will be understood that in systems of larger capacity additional code jumpers will be provided and selected on one or more additional steps of the step- I ping relay bank. The above typical example il- With lever ISML in its normal position as illustrated, relay PC is picked up during the second off period (in order to make the second impulse over a circuit extending from front contact 48 of relay OC, front contact 49 of relay 0, back contact of relay 3V, front contact 52 of relay 2V, conductor I8, front contact I! of relay CD, lever ISML in its normal position and winding of relay PC to In the event that lever ISML is in its reverse dotted line position, then relay NC is picked up to apply a impulse to theline circuit during the second on period.

With lever 2SML in its normal position as illustrated, the second off period is rendered short because relay LG is not picked up during this off period, so that the line is energized to mark the beginning of the secondon period when relay 4E drops to close back contact 32. In the event that lever 2SML is in its reverse dotted line position, then relay LG is picked up over a circuit extending from front contact 48 of relay 00, front contact 49 of relay C, back contact 59 of relay VP, back contact I6 of relay 3V, front contact I5 of relay 2V, conductor I4, front contact I3 of relay CD, lever ZSML in its reverse dotted line position, winding of relay LG and front contact 28 of relay SE to In this case relay LG maintains the line circuit open for a comparatively long interval of time to provide a long 01f period between the first and second impulses in the same manner as previously explained in connection with the first off period.

From the above it will be seen that the impulses applied to the line circuit begin with a impulse-for conditioning purposes when the cycle is initiated from the control ofiice, with the following impulses being or and the time spaces between these impulses being long or short,

dependent upon the code jumper and control lever 5 connections as rendered efiective by the particular code determining relay which is picked up for that cycle.

Station'selectionjor czmtroZs.-It will be obvious that the impulses and the time spaces be- 10 ,tween impulses are, received at all of the field stations, since the field station line relays are all included in-the line circuit However,for convenience in describing the operation of station selection, reference will be made to Figs. 2, 2A, and

previously explained, which code is, first offi'20 long and first on The 'illustratedfield station is rendered responsive to this particular c'ode because of the connections of jumpers 290,

2M, and 202 as illustrated.

The conditioning impulse applied to thet line circuit actuates the polar contacts of relay F to the right. A circuit is now closed for picking up relays SO and SOS which extends from back contact 203 of relay SE contact 204 of relay F in its-right hand dotted position, con- '30 ductor I92, back contact 205 of relay L, back'con- 'tacts -206,2Il:1 and 2Il8 of relays 3V 2V and IV respectively and the upper windings of relays SO and SOS in series to A circuit is now closed for picking up relay FP which extends from contact 222 of relay F in its right hand dotted position; back contact 224 ofrelayLO conductor-I93, front contact 225 of relay SO, conductor I94 and winding of relay FP to Relay SA is picked up over an ob- 40 1 viouscircuit closed at front contact 226 of relay FP and relay SE is-picked up over an obvious circuit closed at front contact 221 of relay SA The picking up of relay SB closes a stick circuit for relay SO which extends from front contact 203 of relay SE conductor I95, front contact -2I4 of'relay SOS, front contact 2I5 and lower winding of relay S0 to A stick circuit is also closed for relay SOS which extends from front contact 2030f relay SB front co tact 2I'I ofrelay FP conductor I96, front contact 2I6-and lower winding of'relay SOSto The picking up of relay SO applies byway of itsfront contact 299 and conductor I8I to contact, 294 of relay F to replace the which is opened at back contact 203 of relay SB This at front contact 2090f relay S0 is applied to the selecting circuit for this relay as will be later-pointed out, so that the dropping of an S0 relay during a cycle rules out the particular station with which this SO relay is associated, because the. original pick-up circuits for the SO relays extend through back contacts of the SB relays, such as back contact 293.

It will be understood that the intermittent energization of relay SA by contact 226 of relay FP supplemented during a long off by contact I89 of relay T, are at such a rate that relay SA ,does not have time to drop out during an operating cycle. It .will also be understood that the is energized. Itwill further, be understood that similar circuits are established at all other field stations for picking up the associated SO and SOS relays and thatthe same operations take place at these other stations during the conditioning on period. a The S0 relays are dropped at theseother stations during the station selection portion of the code and maintained picked up at the illustrated station in response to the assumed station selecting code.

At the illustrated station, relay FP repeats the operations of relay F over the above described pick-up circuit, including front contact 225 of relay SO, when contact 222 of relay F is in its right hand dotted position. When contact 222 is in its left hand position the energizing circuit for relay fP extends through front contact 223 of relay SE During the conditioning on period, relay VP is picked up over a circuit which is not shown but which is similar to the pick-up circuit for relay VP in the control office.

Relay T is picked up during the conditioning on period over a circuit which extends from (-]-),'front contact 2|8 of relay SE front contact 219 of relay FP conductor I9! and winding of relay T to RelayT is somewhat slow in pickingup so that a circuit is effective for pick ing up relay L before relay T picks up, which circuit extends from front contact 2| 8 of relay SB conductor I98, back contact 228 of relay T and winding of relay L to Relay L closes a stick circuit for itself which extends.

contact 236 and winding of relay L to When the line circuit is deenergized to mark the end of the conditioning on period and the beginning of the first off period, the polar contacts of relay F (and of course the polar contacts of the line relays at all other stations) are restored to their neutral positions. The opening of contact 222 of relay F drops relay FP which is effective to pick up relay IV over a circuit which is not shown but which is similar to the corresponding circuit in the control office.

Relay S0 is stuck up during the first off period by means of a circuit closed at back contact 2! l of relay FP which circuit extends from front contact 203 of relaySB back contact 2H of relay FP conductor I80, front contact 215 and lower winding of relay S0 to Relay SOS is deenergized when relay FP is dropped during the first off period because of open front contact 211 of relay PP and because of open contact 2% of relay F The dropping of relay FP during the first off period effects the dropping of relay L because of open front contact 229 of relay FP since back contact 228 of relay T is also open. The opening of front contact 2H3 of relay FP deenergizes relay T, but since this relay is slow releasing'it will maintain its contacts picked up for a comparatively long interval of time. Since the first off period is long and since the drop-away time of relay T is less than the length of a long offperiod, relay T will drop away beforethe line circuit is energized to mark the end of the first off period and the beginning of the first on period. The dropping of relay T closes a circuit at back contact 228 for again picking up relay L.

At the end of the first off period and the beginning of the first on period the energization of the line circuit causes relay F to actuate its polar contacts to the left, which in e relay L was picked up during the first long off period it is maintained stuck up throughout the next (first) on period. It will be apparent that a short off period would not permit the dropping of relay T because the drop-away time of this relay is longer than a short 0155 period.

When relay T is not permitted to drop during an off period (short), then after relay L is dropped by the opening of front contact 229 of relay FP it cannot be again picked'up during this off period so that it is maintained in its dropped away position throughout the next on period.-

From the above it will be observed that relay T detects the length of an off period by dropping during a long off and remaining picked up during a short off, and that relay L stores.

this detected condition throughout the succeeding on period by remaining picked up throughout the succeeding on in response to a preceding long off and remaining down throughout the succeeding on in response to a preceding short off.

The first selection in response to the station selection code is made during the first on period when relay FP is picked up. In the example assumed the long off and on code closes a selecting stick circuit for relay SO which extends from front contact 209 of relay SO, conductor l8l, contact 204 of relay F in its left hand position, conductor I 32, front contact 23I of relay L, back contacts 232 and 233 of relays 3V and 2V respectively, front contact 234 of relay W code jumper 202 in its full line position and upper windings of relays SO and SOS to It will be observed that jumper 202 in its dotted line position would render the above described selecting stick circuit for relay SO incomplete so that this relay would be dropped out when relay FP opened its back contact 2". With the selecting stick circuit complete however, relay S0 is maintained energized and relay SOS is picked up and the stick circuit for relay SOS is again completed by way of front contact 2|! of relay FP The picking up of relay SOS likewise again completes the stick circuit for relay SO by way of front contacts 2M and 2I5.

From the above it will be observed that a first code comprising a short off and a on will be ineffective to maintain relay SO energized during the selecting period because of jumper 26!) not connecting to the SO relay circuit. Likewise a first code comprising a long off and a on will not energize relay SO because of jumper 20! being in its open circuit position. It will thus be apparent that relay S0 at the station to be selected is maintained energized by a composite code made up of the polarity of the first'impulse and the length of the time space preceding this impulse as repeated by relays F and L.

With the provision of two separate code jump- I ers in the'ofiice as illustrated, four different code.

combinations are possible on the first step of the cycle, three of which may be employed for station selection, with thefourthbeing used for the phantom control code call. It is obvious that the systerm will transmit a normally short off and a on at the first step if no CD relay in the office is picked. up as a result of the system being initiated from a field station. No Station must be selected in response to this code and therefore front contact 235 of relay IV is not connected to a code jumper, since this contact is the one selected by the phantom code when a single station code selecting step is provided. It will be obvious that, in the event of two station selecting steps, this front contact 235 will lead to a jumper and the front contacts illustrated in connection with the four code circuits of relay 2V will be used to provide a total of station selection codes, that is 4X4 minus 1, the sixteenth being the phantom code.

In the above example it will be obvious that three stations may beselected on a single step of the system and that the second station will be responsive to a long off and a on code. At this station the jumper corresponding to jumper 2B! of Fig. 2A will be connected in its lower position and the other two jumpers will be in their upper positions. The third station will be responsive to a short off and a on code and at this station the jumper corresponding to 200 will be in its lower position and the other two jumpers will be in their upper positions.

It will be ovious that the long off and 'on station selecting code will be determined in the oflice by two jumpers selected by the associated CD relay similar to jumpers I0 and II of Fig. 1C, with the jumper similar to jumper Ill being connected to the PC bus and with the jumper similar to jumper I! being connected to the LG bus. Likewise the short off and on code will be provided in the control ofiice by having the jumper for this station, similar to jumper I 0, being connected to the PC bus and the jumper similar to jumper Ii being disconnected from the LG bus.

The succeeding impulses of the cycle will be effective to govern the control relays of the selected station only. Upon the picking up of relay 2V at the selected station in response to the second off period, a stick circuit is provided for relay SO which is maintained complete throughout the remainder of the cycle. This is conveniently referred to as the permanent stick circuit and extends from front contact 203 of relay SE conductor I95, front contact 236 of relay 2V front contact 2I5 and lower winding of relay S0 to Relay SOS is dropped out during the second off period when relay FP is released, because of its open front contact 2|! and because there is no circuit including the upper windings of the SO and SOS relays energized after relay 2V is picked up. Relay SOS therefore remains deenergized throughout the remainder of the cycle.

Transmission of controls.It will be recalled that the second off period was normally short because lever 2SML in its normal position was not effective to pick up relay LG during this off period and also that the second on period was because lever ISML in its normal position effected the picking up of relay PC. I'ne (-I-) impulse is received at the illustrated station by line relay F positioning its polar contacts to the right. This closes a circuit for energizing switch machine control relay ISMR which extends from front contact 269 of relay SO, conductor I8 I, contact 204 of relay F in its right hand dotted position, conductor I92, back contact 23'! of relay 3V front contact 238 of relay 2V conductor 239 and upper winding of relay ISMR to Current through the upper winding of this relay positions its polar contact to the right for energizing the normal circuit of switch machine ISM for controlling the position of track switch ITS- to its normal position. In the event that lever ISML is in its reverse dotted line position, then the second impulse will be and relay F will close a circuit at contact 204 in its left hand position, conductor I82, back contact 240 of relay 3V front contact 24! of relay 2V conductor 242 and lower winding of relay ISMR to Current through this winding of switch machine control relay ISMR positions its polar contact to the left for causing the switch machine to actuate the associated track switch to its reverse position.

The second normally short off period is terminated and relay FP is picked up to reenergize relay T before its release, so that relay L remains down throughout the second on period in response to this normally short preceding off period. A circuit is closed for actuating the polar contact of relay 2SMR to its right hand position which extends from front contact 243 of relay FP conductor I83, back contact 244 of relay L, back contact 245 of relay 3V front contact 246 of relayZV conductor 24! and lower winding of relay 2SMR to In the event that lever 2SML is in its reverse position, then relay LG will be picked up to render the second off period abnormally long, so that relay L will remain picked up throughout the succeeding on period (in a manner described in connection with the first on period) to complete a circuit for actuating the polar contact of relay ZSMR to its left hand dotted position, which circuit extends from front contact 243 of relay FP conductor I83, front contact 244 of relay L, back contact 248 of relay 3V front contact 249 of relay 2V conductor 250 and upper winding of relay 2SMR to The polar contact of relay 28MB. in its right hand position causes switch machine ZSM to position track switch ETS to its normal position and with this contact in its left hand dotted position switch machine 28M positions track switch 2T5 to its reverse position.

In a similar manner additional steps may be used for transmitting additional controls to the illustrated field station for governing signals, but since the above typical examples illustrate the manner of such transmission it is believed unnec essary to illustrate the signal control relays which may obviously be controlled by the following polar impulses and time space lengths. Although the four code control circuits used for selecting the station in the manner previously described are shown connected through contacts of the 3V and 2V relays, it will be understood that where station selection is effected on the first step of the cycle these circuits need not connect through contacts of relay 3V it only being necessary that they be broken by back contacts of relay 2V The contacts associated with these circuits on the 2V and 3V relays are shown only for the purpose of indicating that they may be used for station selection in a system where such selection requires more than one step of the cycle and in this event of course the control circuits for controlling the switch control relays, and the like just described, will be transferred to additional stepping relays of the bank.

Following the application of the last impulse the line circuit is deenergized for a comparatively long interval of time referred to as the clearing out period. During this clearing out period of relay SE relay FP remains down sufficiently long to effect the dropping of relays SA and SE in sequence, because of open front contacts 226 and 221 of relays FP and 8A respectively. Relay T is dropped out during this clearing out period because of open front contact 2l9 of relay FP The closure of back contact 228 of relay T will eifect the picking up of relay L because of closed front contact-2H3 of relay SE but relay L will be released when relay 8B releases and opens front contact 2I8. This operation of relay L is of no consequence.

The stepping relays at the field station are dropped out in the same manner as explained in connection with those at the control office, except that their stick circuits are controlled by relay SB Relay S0 is deenergized during the clearing out period when its permanent stick circuit is deenergized at open front contact 203 When the line circuit is reenergized at the end of the clearing out period, relay F again positions its polar contacts to the left and the system is thereby placed in its normal condition.

During the operation of the control cycle above described, relay PT is dropped out during the conditioning on period because of open back contact 223 of relay SE but the release of relay PT serves no purpose during a control cycle. Its function will be explained in connection with an indication cycle. Following the clearing out period, when the line circuit is reenergized, relay PT is picked up over the circuit including contact 222 of relay F in its left hand position. The system is now in its normal condition from which it may be again initiated.

Transmission of indicati0 ns.-Although this system is of the coded duplex type and indications may be transmitted from any station to the control office during the same cycle that controls are transmitted to the same or some other station. it is convenient to first explain the communication of indications alone on a separate operating cycle, before considering the duplex feature of the system.

The manner in which field stations are allowed to transmit only one at a time in a predetermined order will be explained in connection with the look-out feature, this feature being included in the description following the description of the operation of the system with respect to the transmission of indications from a single field station, assuming that such field station is the only one having new indications to transmit at the beginning of the cycle.

Automatic start-A change in the condition of the detector track section or a change in condition of other traflic controlling devices at the illustrated station may occur for effecting the initiation of the system for the transmission of indications. Although the detailed circuits are not shown, it will be assumed (and readily understood) that any such change may so condition these circuits that relay CH is dropped. The dropping of relay CH. closes a circuit for picking up relay PB which extends from back contact 203 of relay SE contact 204 of relay F in its left hand position, conductor I82, back contact 21%| of relay L, back contacts 25!, 252 and 235 of relays 3V 2V and IV respectively, back contact 253 of relay CH, conductor I84, back contacts 254 and 255 of relays L0 and FF respectively, front contact 256 of relay PT and winding of relay PB to Relay PB closes a stick circuit for itself which extends from front contact 25'! of relay PT front contact 258 and winding of relay P3 to The picking up of relay PB opens the normally energized line circuit at open back contact '22l, which effects the dropping of relay F Relay PT is deenergized because of open contact 222 and relay PT drops after a comparatively long interval of time due to its slow-acting characteristics.

The opening of the line circuit also effects the dropping of relay F in the control office, which closes a circuit for picking up relay CF extending from back contact 94 of relay 5E, conductor 15!, back contact 95 of relay F, back contacts 64 and of relays SD and C respectively and lower winding of relay CF to Relay CF closes a stick circuit for itself extending from front contact 45 of relay SC, front contact 96 and upper winding of relay CF to and since relay SB picks up and closes its front contact 93 before relay SC drops and opens its front contact 45, this stick circuit is maintained throughout the cycle but is deenergized during the clearing out period for dropping out relay tending from back contact 36 of relay SD,

dropped during the clearing out period in the same manner described in connection with a control cycle. The opening of back contact 38 of relay CF deenergizes relay NC and relay PC is picked up over a circuit extending from front contact 48 of relay 00, back contact 49 of relay C, front contact 91 of relay CF, back contact 98 of relay IV, PC bus 54 and winding of relay PC to The dropping of relay NC and the picking up of relay PC energizes the line circuit with energy, which is effective to pick up relays F and F? in the control office in a manner already described in connection with a control cycle.

The E relays and the slow-acting relays in the control office are now operated during the conditioning on period in the same manner as described in connection with a control cycle, following which the line is impulscd and the stepping relays at the office and at the transmitting field station are operated in s'ynchronism. During this cycle all of the impulses will be (following the conditioning impulse), because NC bus 40 will be permanently energized when relay lV picks up and closes its front contact 9B. The time spaces between impulses will be normally short because no CD relay is picked up to complete an energizing circuit for relay LG. This series of impulses and normally short time spaces comprises the phantom control code previously mentioned which is ineffective to select any station for controls.

Referring again to the field station, the energization of the line circuit during the conditioning on period causes relay F to position its polar contacts to the right. Relays SO and SOS are picked up but are dropped out in response to the phantom control code. A circuit is now closed for picking up relay L0 which extends from back contact 203 of relay 5B contact 204 of relay F in its right hand dotted position, conductor E92, back contact 205 of relay L, back contacts 236, 201, and 259 of relays 3V 2V and W respectively, conductor I85, front contact 26! of relay PB and winding of relay L to Relays FP and SA are picked up in the manner previously described, but relay 8B is not energized at this time due to open back contact 26! of relay PE The picking up of relay L0 energizes the stick circuit of relay PB over a circuit extending through back contact 262 of relay SA and front contact 263 of relay L0 which circuit is deenergized when relay SA picks up because relay PT will be down at this time, therefore relay PB is deenergized and after a comparatively long interval of time it is released.

The picking up of relay SA closes a stick circuit for relay L0 extending from front contact 284 of relay SA front contact 265 and winding of relay L0 to which stick circuit is maintained energized for holding relay L0 picked up until the clearing out period at the end of the cycle, when relay L0 is released by relay 8A opening front contact 264. When relay PB drops and closes its back contact 26| the energizing circuit for relay SE is completed and this relay picks up and remains up until the clearing out period at the end of the cycle.

Relay PT remains down throughout the cycle and is again energized during the clearing out period. Relays T, L, FP and the stepping relays are operated as in. a control cycle, but the stepping relay bank at the transmitting station only is operated, because front contact 265 of relay SO and front contact 261 of relay L0 will both be open at other stations, so that the stepping relay circuit extending from at a, front contact similar to contact 268 of relay SB and back contacts similar to contact 269 of relay FP' will be ineffective at stations not selected for controls or for the transmission of indications during the cycle.

The stepping relay bank at the transmitting station is operated however because of closed front contact 261 of relay L0 and it will be understood that, in the event of a duplex cycle where some other station is selected for controls, its SO relay will be picked up so that a contact similar to 266 will be closed for permitting operation of the'stepping relay bank at that station.

Registration of a field station.-At the particular station having indications to transmit, lockout relay L0 is up and, because of its open back contact 293, the transmitting contacts 215 and 285 of the FZ and BZ relays are rendered effective. Similarly, by the closure of its front contacts 210 and 2" of relay LO the control circuits for the transmitting relays PF FZ and BZ are rendered effective.

It will be understood that relay 8A at the end station (see Fig. 2B) is picked up during the conditioning on period so that the converter is started by the closure of front contact 322. This effects the application of alternating current to the line circuit by way of transformer TF and this current finds a low impedance path from the right hand terminal of the secondary winding of transformer TF by way of back contact 323 of relay L0 to line conductor R From the left hand terminal of this transformer winding a low impedance path is provided by way of back contacts 320 and 32l of relays PF and PB respectively and the band pass filter, including inductances BIN and 2IN and condensers 1C and 2C to conductor L This alternating current finds a low impedance path through any other stations which may be located between the end station and the transmitting station, similar to that just pointed out at the end station, so that a substantial alternating current potential appears on conductorsR. and L of Fig. 2.

It will be assumed that the transmitting station identifies itself in the control office by a code comprising no alternating current during the conditioning on period, no alternating current during the first off period, alternating current during the first on period and a short first on period. This code combination positions the polar contacts of relays IPT to 4PT inclusive of Fig. to the positionsillustrated. These contacts in their illustrated positions may effect the picking up of a station relay to identify the transmitting field station, but in the drawings this stationrelay is not shown. However, a succeeding code circuit is illustrated as being connected through the polar contacts of these pilot relays in their illustrated positions to indication receiving relay IIR, since this provides means for illustrating how an indication is transmitted and selectively received in the control oflice in accordance with the positions assumed by the pilot'relays. The station identifying code is provided at the transmitting field station by jumpers 2l0 to 2E3 inclusive illustrated in Fig. 2A. It will now be explained how the code combination is provided by the particular jumper arrangement illustrated, and it will also be pointed out how alternate positions of each of these code jumpers select the alternate code for providing a choice of two code combinations for each jumper shown. It will be understood that, in systems of larger size, additional code jumpers will be provided and selected at additional steps of the cycle.

Code jumper 2H connected as illustrated in Fig. 2A determines that no alternating current shall be permitted to flow over the line circuit to the control office during the conditioning on period. This is brought about by picking up relay FZ during the conditioning on period over a circuit extending from jumper 2; back contact 212 of relay IV conductor I86, winding of relay FZ and front contact 2' of relay L0 to This pick-up circuit for relay FZ is completed as soon as relay L0 is picked up during the conditioning on period and upon the picking up of relay FP during this same period a stick circuit is completed for relay FZ which extends from front contact 213 of relay FZ front contact 274 of relay F1 winding of relay FZ and front contact 2' of relay L0 to During the first off period, the dropping of relay FP opens the stick circuit for relay F2 and the picking up of relay IV opens the pickup circuit of relay FZ at back contact 212, thus effecting the release of relay FZ The alternating current connected to conductors L and R of Fig. 2, as previously explained, is by-passed or shunted at the transmitting field station during the conditioning on period in accordance with code jumper 2H in its illustrated position. This shunt circuit extends from conductor R front contact 215 of relay FP front contact 216 of relay F2 inductance 3IN condenser 3C and resistance 4R to conductor L. It will be understood that this is a series resonant shunt circuit offering a minimum impedance to the frequency of the alternating current applied to the line circuit at the end station. Furthermore, a parallel resonant circuit is provided by inductance IIN and condenser IC which traps or blocks out any of the alternating current not shunted by the above described shunt circuit. 

